I have always been nervous at using Thunderbird as I don’t know if you can revert back if you don’t like it. I have a gmail account, a business account off my website accessed by Microsoft Outlook and a GMX account which I have to sign into each time on their website. Can all these be aggregated onto Thunderbird?
Rod, Thunderbird is an e-mail client program similar to Outlook Express or Microsoft Mail. You can choose to stop using it at any time and switch to another e-mail client or choose to use no e-mail client at all. When you set it up, you can have it access multiple accounts if you choose.
This article explains how to set Thunderbird up with Gmail  and tell you where to download the program for free.